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Cognitive Radio Networks have changed the communication paradigm by opportunistically using available spectrum. In such networks, Secondary User vacates the channel when it detects the Primary User. The frequent channel switching degrades the throughput of Cognitive Radio Networks. Current schemes suggest only the selection of Primary Channel if there is not any licensed user available. We propose...
The paper introduces proactive integrated handoff management (IHM) scheme in cognitive radio mobile ad hoc networks (CR-MANETs) through an established route. This scheme considers the primary user (PU) activity, secondary user (SU) mobility and channel heterogeneity in the spectrum handoff decision. To reduce the handoff delay, handoff thresholds are used. When the spectrum handoff cannot be done...
This paper presents a study of mobile wireless LAN (WLAN) hotspots which are used to provide cellular-WiFi tethering service to personal devices. A dense deployment scenario for fixed and mobile WLAN is described and potential performance problems due to interference are identified. An analytical model for coexisting fixed and mobile WLAN hotspots with heterogeneous traffic is presented. The model...
For reducing the channel switching frequency due to uncertain and frequent primary users' interruptions, we design a nonparametric channel allocation algorithm which can effectively manage the spectrum resources in distributed cognitive radio networks and serve for delay-sensitive data traffics. In the proposed algorithm, an infinite Gaussian mixture model is used to get the posterior decision from...
Local area deployments in general and femtocells in particular have proved to be an effective solution for providing ubiquitous coverage in a cost-efficient manner, satisfying the high data rate and QoS requirements for LTE-Advanced systems. In this paper, we investigate inter-cell interference management schemes for dense local area deployments. We propose a distributed capacity based channel allocation...
OFDMA (Orthogonal frequency division multiple access) based systems have been considered as a candidate for future wireless communication systems. In such a system, it is important to provide high data rate services for users with high mobility. For this purpose, decision-directed channel tracking (DDCT) techniques have been investigated for OFDM systems in high mobility environments. The performance...
Wireless networks are characterized by having limited resources accessed by a large number of mobile stations with distinct capabilities. In such challenged environment the dynamic control of resources is of major importance to mitigate the limitations of wireless networks, such as the impact of low data rate stations and wireless channel oscillations. Such augmented usage of wireless resources can...
Researches about multi-radio mesh networks have mostly focused on channel allocation under internal interference. However, the deployment of WMNs in unlicensed bands of dense urban areas imposes many challenges regarding co-existence with residential access points. In this paper, we propose Urban-X, which is a first attempt towards a new architecture for MultiRadio Cognitive Mesh Networks. We develop...
A central scheduling problem in wireless communications is that of allocating resources to one of many mobile stations that have a common radio channel. Much attention has been given to the design of efficient and fair scheduling schemes that are centrally controlled by a base station (BS) whose decisions depend on the channel conditions of each mobile. The BS is the only entity taking decisions in...
Downlink scheduling schemes are well-known and widely investigated. In the multiuser MIMO (broadcast) case, downlink scheduling in the presence of non-perfect CSI is only scantly treated. In this paper we provide a general framework within which the problem can be addressed systematically. Then, we focus on the special case of proportional fairness and ??hard fairness??, with Gaussian coding and linear...
To ensure the access point (AP) based quality of service (QoS) especially for multimedia communications, it is important to know the Bandwidth performance of a transmission media. And the limitation of existing fixed channel allocation caused the degradation on overall throughput of the wireless local area network (WLAN). This paper proposes a new bandwidth estimation technique and dynamic channel...
Opportunistic scheduling and rate-adaptation mechanisms exploit the variations in the channel states experienced by different users through the allocation of resources to users with better channel quality. Opportunistic scheduling has been considered in various contexts, typically with the assumption that rate adaptation and channel reassignment can be implemented with no delay, based on the instantaneous...
This paper addresses practical implementation issues of resource allocation in OFDM A networks: inaccuracy of channel state information (CSI) available to the resource allocation unit (RAU) and diversity of subscribers' quality of service (QoS) requirements. The resource allocation problem in the considered point-to-multipoint (PMP) network is modeled as a network utility maximization (NUM) problem...
The network planning aims to allow the maximum number of users and throughput in a network. This imposes a demanding performance requirement on the new relay-based architecture for mobile WiMAX, in which the capacity estimation is complex. In the network design process, where interference avoidance plays an important role, WiMAX supports reconfiguration of the subchannel usage with some frequency...
Dense deployments of hybrid WLANs result in high levels of interference and low end-user throughput. Many frequency allocation mechanisms for WLANs have been proposed by a large body of previous studies. However, none of these mechanisms considers the load that is carried by APs in terms of channel conditions, number of affiliated users as well as traffic-load, in conjunction. In this paper, we propose...
We address the problem of improving the throughput in multi-hop ad hoc networks. Many approaches can be considered to address this issue. We focus on those that imply the use of multiple radio interfaces with separate radio channels. In this context, we need to address two important issues, namely channel assignment and routing. We propose a throughput-oriented scheme called IC2A2R. It allows nodes...
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